Though the Journeymen of the Design Department argued quite extensively about the booster modules of the Disruptor Project, they had good reasons to focus on this aspect.
Light mechs depended heavily on mobility to perform their roles on the battlefield. This was even more important for their expert mech versions as it was literally the only reason why they were able to survive in fights against other deadly expert mechs.
The opponents that Venerable Tusa would face in the future were far different from the dummies he encountered during his most recent campaign.
His battles back on Prosperous Hill VI were no different from bullying children in his perspective. The biomechs he faced were sometimes decent, but were mostly lower-end models that could not keep up with the performance of a military-grade mech.